Command guidance and tracking system



Dec. 3, 1963 Filed Aug. 15. 1960 P. E. FISKE COMMAND GUIDANCE AND TRACKING SYSTEM 2 Sheets-Sheet 1 OSCILLATOR EER??? z i p FIXED DELAY GATE TRANSM'TTER l6 F, I GATE 4- /8 2/ I I9 7 R l I COMMAND COMMAND RECEIVER Z 3 DECODER CONTROL BOX FREQUENCY PULSE VARIABLE VARIABLE OSC'LI-ATOR DIVIDER SHAPER DELAY DELAY CODER l I l TRANSMITTER A38 I 3.9 F 2 RANGE ,g READER 4/ 43 VARIABLE RECEIVER DELAY INDICATOR INVENTOR.

PAUL E F/SKE M @MAW Dec. 3, 1963 P. E. FISKE 3,113,291

COMMAND GUIDANCE AND TRACKING SYSTEM Filed Aug. 15, 1960 2 Sheets-Sheet 2 Z O I I I Z O Fig. 3

INVEN TOR. PAUL E F/SKE United States Patent The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a command guidance and tracking system and more particularly to a command guidance and tracking system utilizing extremely short periods of transmission.

The need for interrogating a controlled station, such as a guided missile, to secure range information could theoretically be eliminated by providing extremely stable and carefully synchronized pulse signal generators in both the missile and the controlling station. Under these conditions, if the missile were at zero range from the controlling station there would be no time difference between the pulses sent out from the missile generator and those generated at the controlling station. As the missile moved away, however, the pulses arriving at the controlling station would be delayed in time by the missiles transit time, allowing the range to be measured between the pulses generated at the controlling station and arriving from the missile without the necessity of interrogating signals. The missile bearing could be measured by standard means, i.e., directional receiving antennas.

This use of synchronized pulses in both the controlled and controlling stations would also allow relatively secure command signals to be sent from the controlling station to the missile. This can be done by gating a decoder located in the. missile to receive commands from the controlling station for short intervals only. These intervals can be spaced with extremely close tolerance with reference to the synchronized pulses available at both the controlling station and the missile as outlined above.

According to the invention, the two pulse generators, i.e., one in the missile and one in the surface equipment, are synchronized in phase before the missile is launched. The pulse generator in the output of the missile is passed through a fixed delay line and a gate to key the missile transmit-ting equipment. The input to the fixed delay also supplies an on pulse to a second gate and the output of the fixed delay supplies an off pulse to this second gate.

7 The receiver in the missile for receiving command signals has an output also coupled to the input of this second gate. Thus, the missile can only receive command signals during the delay period, i.e., the gated period of the second gate. This feature coupled with the necessity of having the properly coded signal renders jamming of the missile practically impossible. If for some reason the two signal generators drift, one with respect to the other, and the time slot during which the missile can receive signals is lost, a second feature enables synchronization after missile launching. This is accomplished by taking another output of the missile receiver through a reply unlock decoder which can receiver signals at any time but will only be unlocked by a definite code pattern.

- When this code pattern is presented, any further signals from the receiver will key the missile transmitter directly for an extremely short period. This enables synchron- 3,1 H191 Patented Dec. 3, .1963

mal operation, i.e., once the missile is determined to be on course, a command signal would be sent turning oif all missile radiation for a predetermined period of time, at which time the missile would be allowed to transmit further signals to facilitate checking the projectory path.

The surface equipment as previously mentioned has a pulse generator identical to the pulse generator in the missile equipment. The output of the pulse generator is passed through a variable delay network which is utilized to synchronize the two signal generators in phase relationship at zero range. delay network is passed through a second variable delay network and a coder to the surface equipment transmitter keying circuits. The second variable delay is utilized to initially delay the pulses one period in conjunction with the inherent delay of the coder. The output of the coder is also passed through a third variable delay and to the input of the surface equipment indicating console as a trigger for the indicator sweep circuits. The output of the third variable delay circuit is also passed to the indicating console for display therein. As the missile moves away, its self keyed transmitted pulse is picked up by the surface equipment receiver and indicated on the surface equipment indicator simultaneously with the third delay output. If the second variable delay is adjusted so that the output from the coder coincides with the received transmissions from the missile, the delay in the second delay circuits will represent the transit time from the missile to the surface equipment. The third variable delay is then coupled mechanically to the second variable delay so that its output when compared to the output of the coder will represent the range of the missile. It is apparent at this point that once the two pulse generators are synchronized, no interrogations are necessary to secure range information.

When a command signal is sent to the missile from the ground equipment, the last pulse of the command signal will key the missile transmitter a set period of time prior to the missile self-triggered pulse. This is accomplished by use of the extremely accurate time slot as determined by the first gate, during which the missile must be interrogated, and the coding signal in conjunction with the decoder in the missile equipment. Thus, every time a command signal is sent to the missile, the missile will transmit a pulse which should be followed by a selftriggered pulse within the missile a set time later. If the time in between these received pulses at the surface equipment is not the set time, variable delay number one It is thus an object of the present invention to provide a command guidance and tracking system in which ranging can be accomplished with a minimum of interrogating signals.

A further object is the provision of a command guidance and tracking system which is extremely difficult to jam.

Another object of the present invention is to provide a command guidance and tracking system requiring a minimum of operator skill and experience.

A still further object of the invention is to provide a command guidance and tracking system in which the transmissions of both the surface station and controlled station are extremely short.

Yet another object of the present invention is to provide a command guidance and tracking system in which all transmissions from the controlled station can be eliminated for predetermined periods of time.

A still further object of the present invention is the provision of a command guidance and tracking system The output of the first variable- 1? which provides for an acknowledgment from the controlled station of all command transmissions.

These and other objects of the present invention will become readily apparent and understood with reference to the following detailed description taken in conjunction with the drawings, in which:

FIG. 1 is a block diagram of the controlled station equipment;

FIG. 2 is a block diagram of the surface station equipment; and

FIG. 3 is a graphic representation of signals present in both the controlled and surface equipment in time relationship to one another.

Referring to FIG. 1, there is shown oscillator 11 coupled to frequency divider 12, which in turn is coupled to pulse shaper 13. The output of pulse shaper 13 is coupled to fixed delay 14 and gate generator 16. The output of fixed delay 14 is coupled to gate 17 and to gate generator 16. The output of gate generator 16 is coupled to command decoder 18, the output of which is coupled to gate 17 and command control 19. The output of command control 19' is coupled to gate 17 and to the guidance controls of the missile. Receiver 21 is coupled to reply unlock decoder 22, the output of which is coupled to transmitter 23. The output from receiver 21 is also coupled to the input of command decoder 18.

Referring to FIG. 2, oscillator 31 is coupled to frequency divider 32, the output of which is coupled to pulse shaper 33. The output of pulse shaper 33 is coupled through variable delay 34 and variable delay 36 to coder 37. The output of coder 37 is connected to the keying circuits of transmitter 38 and to range reader 39, variable delay 41, and indicator 42. The output of variable delay 41 is connected to range reader 39, and indicator 42. Receiver 43 is also connected to indicator 42. Variable delay 36 and variable delay 41 are mechanically ganged as shown by broken line 44.

Referring now to FIG. 3, there are shown waveform sig- 113-15 13, 14 23, 33 34 35 37 41 and 43- Thfise nals are plotted as pulses of voltage vs. time. Times t t and t are indicated by lightly drawn vertical lines which are common to all signals.

Operation Referring back to FIG. 1, oscillator 11 is a crystal controlled temperature regulated oscillator which is extremely stable in frequency. The output of oscillator 11 is divided down in frequency divider 12 to a frequency of 250 c.p.s. in the preferred embodiment. The output of frequency divider 12 is shaped in pulse shaper 13 resulting in the signals shown in FIG. 3 as S occurring at time t This signal is utilized to start gate generator 16 and is also passed through fixed delay 14. Fixed delay 14 in the preferred embodiment is a 400' microsecond delay line, the output of which is coupled to gate circuit 17 and operates to turn gate generator 16 off. A further output of fixed delay 14 shown as S at time t in FIG. 3 is coupled through gate 17 to key transmitter 23. Thus every 4,000 microseconds, in the preferred embodiment, transmitter 23 will send out a pulse initiated by oscillator signal 11.

When a command signal is received in receiver 21 of the proper code, it is coupled to the input of command decoder 18. If this signal is of the proper code and occurs during the gate generated by gate generator 16', it will be passed through command decoder 18 to command control box 19. Command control box 19 is merely a relay matrix which serves to control the guidance function of the missile. Command decoder 13 is designed to pass the last pulse of the incoming signal from receiver 21 as another input of gate 17. This signal, when gate 17 is open, will also pass through gate 17 and key transmitter 23. Thus, during command transmissions from the surface equipment, transmitter 23 will put out two pulses, one at time t which represents the last coded pulse of the command signal and one at time t which represents the output of fixed delay 14. These two transmitted pulses are represented in FIG. 3 at S If the missile equipment becomes unsynchronized with the surface equipment, i.e., oscillator 11 of FIG. 1 is not in phase with oscillator 31 of FIG. 2, a test code can be sent from the surface equipment to receiver 21 which will unlock reply unlock decoder 22. Reply unlock decoder 22 is designed to allow uncoded pulses to pass through, after once being unlocked, for a period of 0.1 second. Thus, after unlocking reply unlock decoder 22, any signal received in receiver 21 will pass through reply unlock decoder for this period, keying transmitter 23. This is to allow resynchronization of the surface equipment, since the spacing between the self triggered pulse transmitted by transmitter 23 and the pulse keyed through reply unlock decoder 22, should still be as represented in a time relationship to t and t This time relationship can be re-established at the surface equipment as will be explained below. A further feature of the guided or missile equipment is the removal of tall transmissions from the missile during a predetermined period of time. A stop transmission signal sent by the surface equipment during the proper time slot as determined by gate 16 will be passed through command decoder 18 and into command control box 19. This specially coded signal Will cause an output from command control box 19 to gate 17 which will turn off gate 17 for a predetermined period of time, as dictated by the timing circuits of command control box 19. In practice this time will be in the order of minutes. Thus, once the missile has been determined to be on course, a stop transmission signal can be sent from the surface equipment which will turn off gate 17 allowing no keying pulses to be passed through gate 17, and, in turn, no transmissions from transmitter 23. Of course, if an emergency arises or any time it is desired a code can be transmitted to unlock reply unlock decoder 22 from the surface equipment which will cause transmissions during the following tenth of a second from transmitter 23, if further interrogated, since this channel bypasses gate 17.

It is pointed out here that all of the blocks shown in FIG. 1 are well within the state of the art and should not require further clarification, i.e., the decoders can be comprised of tapped delay lines requiring a coincidence input and output, etc. Since these do not form a part of the invention per se further clarification is deemed unnecessary.

Referring back to FIG. 2, oscillator 31, divider 32 and pulse shaper 33 are identical to oscillator 11, frequency divider 12, and pulse shaper 13 of FIG. 1. The output of pulse shaper 33 will then be at the same frequency within a very close tolerance of the output of pulse shaper 13 of FIG. 1. This is shown as signal S of FIG. 3. It is noted here that although the frequencies will be identical, the relative phase will be completely undeterminable, since the two oscillators are not synchronized by any external means. The output of pulse shaper 33 is then delayed in variable delay 34. Variable delay 34 is then adjusted to place the output of pulse shaper 33 in exact phase synchronization with the output of fixed delay 14 of FIG. 1, i.e., both signals S and S now appear at time t as shown in FIG. 3. This adjustment is made before launching the missile at zero range. In the preferred emmbodiment, the output of variable delay 34 is passed through a variable delay 36. Variable delay 36 will be utilized to compensate for changes in missile range after launching. At zero range, variable delay 36 is set to delay the output of variable delay 34 to time t At zero range this will correspond then to the output of pulse shaper 13 and is shown as S in FIG. 3. The output of variable delay as is utilized to key coder 37 which can be set to any one of a number of predetermined codes, such as command codes, stop transmission, or reply unlock. Coder 37 is designed to put out pulses which start at t with the last pulse occurring exactly at t as shown in FIG. 3. t in the preferred embodiment is microseconds before t This is shown at S in FIG. 3. Alt this point it is emphasized that the coded output pulses of coder 37 are within the time slot established by gate 16 of FIG. 1. These outputs then key transmitter 38. The last pulse of the output code from coder 37 is passed to the inputs of range reader 3-9, variable delay 41 and indicator 42, respectively.

Variable delay 41 is mechanically coupled to variable delay 36 as indicated by broken line 44. In operation, when the missile is launched, self generated signals within the missile are received in receiver 43 and displayed on indicator 42. The input pulse from coder 37 which occurs at time I is utilized to start the sweep circuits in indicator 42. The output of variable delay 41 is displayed along with the video from receiver 43 on indicator 42. The delay of variable delay 41 is then adjusted to coincide with the video pulse from receiver 43. Variable delay 36 is geared to variable delay 41 in a oneztwo relationship, i.e., the delay of variable delay 36 is decreased at one half the rate variable delay 41 is increased. This will insure that the transmissions from transmitter 38 will arrive in the time slot defined by t and t at the missile regardless of missile range. Since variable delay 41 is adjusted to delay the last pulse output of coder 37 an amount corresponding to the range of the missile, the

range can then be read on range reader 39, i.e., the last pulse from coder 37 starts the range count in range reader 39 and the output pulse from variable delay 41 stops the range count in range reader 39. Obviously, the range can also be calibrated on indicator 42.

If the delay of variable delay 34, 36, and 41 are all adjusted for the range of the missile from the surface equipment, the received pulses from receiver 43 will appear as previously stated at times t and t as indicated by S in "FIG. 3. if the two pulses received in receiver 33 are not 100 microseconds apart, regardless of range, this will indicate that the relative phase of signals S and S have shifted and variable delay 34 can then be adjusted for this 100 microsecond spread. This is due to the fact that when [the missile equipment as shown in FIG. 1 is being interrigated if the phasing and timing have been correctly set, the last pulse received in the missile equipment in decoder 18 will trigger transmitter 23, followed 100 microseconds later by the self-triggered pulse from fixed delay 1*4. If the surface equipment or the missile equipment has drifted this relationship of 100 microseconds will no longer be true and variable delay 34 will have to be readjusted.

Should the equipment drift out of the 400 microsecond time slot as defined by gate 16 of FIG. 1, it will be necessary to code transmitter 38 to unlock reply unlock decoder 22 keying transmitter 23 and establishing a 100 microsecond relationship between that transmission and the automatic keying transmission from fixed delay '14.

Thus, a system [has been described which is extremely difiicult, if not impossible, to jam since both the proper code and time of transmission are required to unlock the command decoder 18 in the missile. 'The extremely short transmission time coupled with the stop transmission operation also makes detection and homing extremely dilficult, if not impossible.

While the invention has been described with respect to a guided missile system it is not limited thereto since it has obvious application and utility in any guidance or ranging system.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. .It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A command guidance and tracking system including a controlled station comprising; a fixed delay means having an input; a first pulse generator having an output connected to the input of said fixed delay means, a gating 6 circuit having start and stop inputs, the output of said first pulse generator being connected to the start input of said gating circuit and the output of the fixed delaying means connected to the stop input of said gating circuit, decoding means having an input, a receiver for receiving electromagnetic transmissions having an output connected to the input of said decoding means, the output of said gating circuit connected to said decoding means tor gating said decoding means, transmitting means for transmitting electromagnetic energj, a first output of said docoding means coupled to said transmitting means for keying said transmitting means, control means for controlling said control station, a second output of said decoding means connected to said control means for controlling said controlled station in accordance with a predetermined command code, and a control station comprising: a second pulse generator at the same frequency of said first pulse generator, a first variable delay means, said second pulse generator having an output connected to the input of said first variable delay means, second variable delay means, said first variable delaying means having an output connected to the input of said second variable delaying means, coding means for generating desired codes, said second variable delaying means having an output connected to the input of said coding means, second transmitting means for transmitting electromagnetic energy, said coding means having a first output connected to a said second transmitting means for keying said second transmitting means, third variable delay means, a second output of said coding means connected to third variable delaying means, indicating means for indicating range to the controlled station, and a third outputof said coding means connected to said indicating means for triggering said indicating means, said third variable delaying means having an output connected to the input of said indicating means for display on said indicating means, and sec ond receiving means for receiving electromagnetic energy.

transmitted by said first transmitting means, said second receiving means having an output connected to the input of said indicating means for simultaneous display on said indicating means, said second variable delaying means and said third variable delaying means having delay mechanisms mechanically coupled in a two to one ratio.

2. The command guidance and tracking system of claim 1 and further including gating means, wherein the outputs of said fixed delaying means and said decoding means are coupled to said first transmitter through said gating means, and said control means has a gate output operable to close said gating means upon receiving a predetermined code from said first mentioned receiver.

3. The command guidance and tracking system of claim 2 and further including a reply unlock decoder, wherein said first mentioned receiver has an output coupled to the input of said reply unlock decoder, and said reply unlock decoder has an output connected directly to said first transmitter keying circuits for keying said transmitter, said reply unlock decoder being receptive to any output of said first mentioned receiver for a predetermined interval after receipt of a predetermined unlock code.

4. A command guidance and tracking system including; a controlled station comprising; a fixed delay means having an input terminus, a pulse generator having an output connected to the input terminus of said fixed delaying means, a gating circuit having start and stop inputs, the output of said pulse generator connected to the start input of said gating circuit and the output of the fixed delaying means connected to the stop input of said gating circuit thereof, a receiver for receiving electromagnetic transmissions having an output, decoding means operatively coupled to the output of said receiver for decoding coded electromagnetic transmissions, the output of said gating circuit connected to said decoding means for gating said decoding means, transmitting means for transmitting electromagnetic energy, said first output of said decoding means coupled to said transmitting means for keying said transmitting means, control means for controlling said controlled station, a second output of said decoding means connected to said control means for controlling said control station in accordance With a predetermined command code.

5. The command guidance and tracking system of claim 4 and further including gating means, wherein the outputs of said fixed delaying means and said decoding meme are coupled to said first transmitter through said gating means, and said control means has a gate output operable to close said gating means upon receiving a predetermined code from said first mentioned receiver.

6. The command guidance and tracking system of claim 5 and further including a reply unlock decoder, wherein said first mentioned receiver has an output coupled to an input of said reply unlock decoder, and said reply unlock decoder has an output connected directly to said first transmitter keying circuit for keying said transmitter, said reply unlock decoder being receptive to any output of said first mentioned receiver for a predetermined interval after receipt of a predetermined unlock code.

7. A control station comprising a pulse generator, said P111156 generator having an output, first variable delaying means operatively coupled to the output of said pulse generator for delaying the output from said pulse generator, second variable delaying means operatively coupled to said first variable delay means for introducing a further delay, coding means operatively coupled to the output of said second delaying means for generating desired codes and having outputs, said coding means having a first output connected to said transmitting means for keying said transmitting means, third variable delaying means, a second output from said coding means connected to said third variable delaying means, indicating means, and a third output from said coding means connected to said indicating means for triggering said indicating means, said third variable delaying means connected to the input of said indicating means for displaying on said indicating means, and receiving means for receiving electromagnetic energy transmitted by a controlled station, said receiving means having an output connected to the input of said indicating means for simultaneous display on said indicating means, said second variable delaying means and said third variabie delaying means having delay mechanisms mechanically coupled in a two to one ratio. I

References Cited in the file of this patent UNITED STATES PATENTS 2,612,601 Musselman Sept. 30, 1952 

1. A COMMAND GUIDANCE AND TRACKING SYSTEM INCLUDING A CONTROLLED STATION COMPRISING; A FIXED DELAY MEANS HAVING AN INPUT; A FIRST PULSE GENERATOR HAVING AN OUTPUT CONNECTED TO THE INPUT OF SAID FIXED DELAY MEANS, A GATING CIRCUIT HAVING START AND STOP INPUTS, THE OUTPUT OF SAID FIRST PULSE GENERATOR BEING CONNECTED TO THE START INPUT OF SAID GATING CIRCUIT AND THE OUTPUT OF THE FIXED DELAYING MEANS CONNECTED TO THE STOP INPUT OF SAID GATING CIRCUIT, DECODING MEANS HAVING AN INPUT, A RECEIVER FOR RECEIVING ELECTROMAGNETIC TRANSMISSIONS HAVING AN OUTPUT CONNECTED TO THE INPUT OF SAID DECONDING MEANS, THE OUTPUT OF SAID GATING CIRCUIT CONNECTED TO SAID DECODING MEANS FOR GATING SAID DECODING MEANS, TRANSMITTING MEANS FOR TRANSMITTING ELECTROMAGNETIC ENERGY, A FIRST OUTPUT OF SAID DECODING MEANS COUPLED TO SAID TRANSMITTING MEANS FOR KEYING SAID TRANSMITTING MEANS, CONTROL MEANS FOR CONTROLLING SAID CONTROL STATION, A SECOND OUTPUT OF SAID DECODING MEANS CONNECTED TO SAID CONTROL MEANS FOR CONTROLLING SAID CONTROLLED STATION IN ACCORDANCE WITH A PREDETERMINED COMMAND CODE, AND A CONTROL STATION COMPRISING: A SECOND PULSE GENERATOR AT THE SAME FREQUENCY OF SAID FIRST PULSE GENERATOR, A FIRST VARIABLE DELAY MEANS, SAID SECOND PULSE GENERATOR HAVING AN OUTPUT CONNECTED TO THE INPUT OF SAID FIRST VARIABLE DELAY MEANS, SECOND VARIABLE DELAY MEANS, SAID FIRST VARIABLE DELAYING MEANS HAVING AN OUTPUT CONNECTED TO THE INPUT OF SAID SECOND VARIABLE DELAYING MEANS, CODING MEANS FOR GENERATING DESIRED CODES, SAID SECOND VARIABLE DELAYING MEANS HAVING AN OUTPUT CONNECTED TO THE INPUT OF SAID CODING MEANS, SECOND TRANSMITTING MEANS FOR TRANSMITTING ELECTROMAGNETIC ENERGY, SAID CODING MEANS HAVING A FIRST OUTPUT CONNECTED TO A SAID SECOND TRANSMITTING MEANS FOR KEYING SAID SECOND TRANSMITTING MEANS, THIRD VARIABLE DELAY MEANS, A SECOND OUTPUT OF SAID CODING MEANS CONNECTED TO THIRD VARIABLE DELAYING MEANS, INDICATING MEANS FOR INDICATING RANGE TO THE CONTROLLED STATION, AND A THIRD OUTPUT OF SAID CODING MEANS CONNECTED TO SAID INDICATING MEANS FOR TRIGGERING SAID INDICATING MEANS, SAID THIRD VARIABLE DELAYING MEANS HAVING AN OUTPUT CONNECTED TO THE INPUT OF SAID INDICATING MEANS FOR DISPLAY ON SAID INDICATING MEANS, AND SECOND RECEIVING MEANS FOR RECEIVING ELECTROMAGNETIC ENERGY TRANSMITTED BY SAID FIRST TRANSMITTING MEANS, SAID SECOND RECEIVING MEANS HAVING AN OUTPUT CONNECTED TO THE INPUT OF SAID INDICATING MEANS FOR SIMULTANEOUS DISPLAY ON SAID INDICATING MEANS, SAID SECOND VARIABLE DELAYING MEANS AND SAID THIRD VARIABLE DELAYING MEANS HAVING DELAY MECHANISMS MECHANICALLY COUPLED IN A TWO TO ONE RATIO. 